Treating Ordinal Data as Continuous

Posted by Laurie Petch on Jan 09, 2007; 10:00am
URL: http://spssx-discussion.165.s1.nabble.com/Treating-Ordinal-Data-as-Continuous-tp1073024.html

Apologies, this is more of a statistical question, though it does have an indirect bearing on SPSS. As subscribers
to this list will know, in psychology it is common practice to treat ordinal level data deriving from rating scales as if
they were continuous data and subjecting them to inferential statistical analysis. The argument I have heard in
favour of doing this is that ordinal data behave much more like continuous data when they are summed and
averaged. I have not seen this argument in writing, however, and would be grateful to anyone who can point me
in the direction of a relevant source.

Also, if anyone can suggest counter-arguments to this justification, that would be great too. It just strikes me that a
score of '120' as opposed to '118' on an anxiety measure is data of a very different kind than someone who is
120cm tall as opposed to 118cm.

To say that ordinal data behave like continuous data is surely rather like saying that, since cheese 'behaves' more
like butter when it is heated, it's okay to use cheese instead of butter to make a cake?

Laurie
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Laurie Petch
Chartered Educational Psychologist (British Psychological Society)